/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.jni;

import java.nio.ByteBuffer;

/**
 * Pool
 *
 * @author Mladen Turk
 */
public class Pool {

	/**
	 * Create a new pool.
	 *
	 * @param parent The parent pool.  If this is 0, the new pool is a root
	 *               pool.  If it is non-zero, the new pool will inherit all
	 *               of its parent pool's attributes, except the apr_pool_t will
	 *               be a sub-pool.
	 * @return The pool we have just created.
	 */
	public static native long create(long parent);

	/**
	 * Clear all memory in the pool and run all the cleanups. This also destroys all
	 * subpools.
	 *
	 * @param pool The pool to clear
	 *             This does not actually free the memory, it just allows the pool
	 *             to re-use this memory for the next allocation.
	 */
	public static native void clear(long pool);

	/**
	 * Destroy the pool. This takes similar action as apr_pool_clear() and then
	 * frees all the memory.
	 * This will actually free the memory
	 *
	 * @param pool The pool to destroy
	 */
	public static native void destroy(long pool);

	/**
	 * Get the parent pool of the specified pool.
	 *
	 * @param pool The pool for retrieving the parent pool.
	 * @return The parent of the given pool.
	 */
	public static native long parentGet(long pool);

	/**
	 * Determine if pool a is an ancestor of pool b
	 *
	 * @param a The pool to search
	 * @param b The pool to search for
	 * @return True if a is an ancestor of b, NULL is considered an ancestor
	 * of all pools.
	 */
	public static native boolean isAncestor(long a, long b);


    /*
     * Cleanup
     *
     * Cleanups are performed in the reverse order they were registered.  That is:
     * Last In, First Out.  A cleanup function can safely allocate memory from
     * the pool that is being cleaned up. It can also safely register additional
     * cleanups which will be run LIFO, directly after the current cleanup
     * terminates.  Cleanups have to take caution in calling functions that
     * create subpools. Subpools, created during cleanup will NOT automatically
     * be cleaned up.  In other words, cleanups are to clean up after themselves.
     */

	/**
	 * Register a function to be called when a pool is cleared or destroyed
	 *
	 * @param pool The pool register the cleanup with
	 * @param o    The object to call when the pool is cleared
	 *             or destroyed
	 * @return The cleanup handler.
	 */
	public static native long cleanupRegister(long pool, Object o);

	/**
	 * Remove a previously registered cleanup function
	 *
	 * @param pool The pool remove the cleanup from
	 * @param data The cleanup handler to remove from cleanup
	 */
	public static native void cleanupKill(long pool, long data);

	/**
	 * Register a process to be killed when a pool dies.
	 *
	 * @param a    The pool to use to define the processes lifetime
	 * @param proc The process to register
	 * @param how  How to kill the process, one of:
	 *             <PRE>
	 *             APR_KILL_NEVER         -- process is never sent any signals
	 *             APR_KILL_ALWAYS        -- process is sent SIGKILL on apr_pool_t cleanup
	 *             APR_KILL_AFTER_TIMEOUT -- SIGTERM, wait 3 seconds, SIGKILL
	 *             APR_JUST_WAIT          -- wait forever for the process to complete
	 *             APR_KILL_ONLY_ONCE     -- send SIGTERM and then wait
	 *             </PRE>
	 */
	public static native void noteSubprocess(long a, long proc, int how);

	/**
	 * Allocate a block of memory from a pool
	 *
	 * @param p    The pool to allocate from
	 * @param size The amount of memory to allocate
	 * @return The ByteBuffer with allocated memory
	 */
	public static native ByteBuffer alloc(long p, int size);

	/**
	 * Allocate a block of memory from a pool and set all of the memory to 0
	 *
	 * @param p    The pool to allocate from
	 * @param size The amount of memory to allocate
	 * @return The ByteBuffer with allocated memory
	 */
	public static native ByteBuffer calloc(long p, int size);

    /*
     * User data management
     */

	/**
	 * Set the data associated with the current pool
	 *
	 * @param data The user data associated with the pool.
	 * @param key  The key to use for association
	 * @param pool The current pool
	 *             <br><b>Warning :</b>
	 *             The data to be attached to the pool should have a life span
	 *             at least as long as the pool it is being attached to.
	 *             Object attached to the pool will be globally referenced
	 *             until the pool is cleared or dataSet is called with the null data.
	 * @return APR Status code.
	 */
	public static native int dataSet(long pool, String key, Object data);

	/**
	 * Return the data associated with the current pool.
	 *
	 * @param key  The key for the data to retrieve
	 * @param pool The current pool.
	 */
	public static native Object dataGet(long pool, String key);

	/**
	 * Run all of the child_cleanups, so that any unnecessary files are
	 * closed because we are about to exec a new program
	 */
	public static native void cleanupForExec();

}
